R. R. Tramontin

Etiology and Pathology of Equine Placentitis

Placentas from aborted, stillborn, and premature foals were examined during the 1988 and 1989 foaling seasons, and 236 of 954 (24.7%) had placentitis. Microorganisms associated with placentitis were isolated or demonstrated from 162 of 236 (68.6%) placentitis cases. Leptospira spp. and a nocardioform actinomycete were 2 important, newly emerging bacteria associated with equine placentitis. Major pathogens identified in decreasing order were Streptococcus zooepidemicus, Leptospira spp., Escherichia coli, a nocardioform actinomycete, fungi, Pseudomonas aeruginosa, Streptococcus equisimilis, Enterobacter agglomerans, Klebsiella pneumoniae, and alpha-hemolytic Streptococcus. Pathogens were not recovered in 64 cases (27.1%) and overgrowth by saprophytic bacteria was recorded in 10 cases (4.2%). Twenty-seven cases (16.6%) had mixed bacterial growth and 93 cases (57.4%) had bacteria cultured from both placenta and fetal organs. The majority of the placentitis cases caused by bacteria, with the exception of Leptospira spp. and the nocardioform actinomycete, occurred in 2 forms. One was acute, focal or diffuse; had an infiltration of neutrophils in the intervillous spaces or necrosis of chorionic villi; was associated with bacteremia; and frequently occurred in the placenta from fetuses expelled before or at midgestation. The other was observed from foals expelled at late gestation, was mostly chronic and focal or focally extensive, and occurred mostly at the cervical star area. Chronic placentitis was characterized by the presence of 1 or a combination of the following lesions: necrosis of chorionic villi, presence of eosinophilic amorphous material on the chorion, and infiltration of mononuclear inflammatory cells in the intervillous spaces, villous stroma, chorionic stroma, vascular layer, and allantois. Chorangiosis, hyperplasia with or without squamous metaplasia of the chorionic epithelim, and adenomatous hyperplasia of the allantoic epithelium were frequently associated with chronic placentitis. Leptospira spp. induced, regardless of gestational age, a diffuse placentitis with the presence of a large number of spirochetes in the stromal tissues. The nocardioform acti-nomycete, a gram-positive, filamentous, and branching bacillus, induced an unique chronic-active focally extensive placentitis located at the base of the horn or at the junction between the body and horn of the allantochorion. Fungi, with the exception of Histoplasma sp. and Candida sp., induced a chronic focally extensive placentitis at the cervical star area similar to that seen in chronic bacterial placentitis. Histoplasma sp. induced a multifocal granulomatous placentitis, and Candida sp. induced a diffuse necrotizing and proliferative placentitis.

Equine abortion and stillbirth in central Kentucky during 1988 and 1989 foaling seasons

Pathologic and microbiologic examinations were performed on 1,211 aborted equine fetuses, stillborn foals, and placentas from premature foals in central Kentucky during the 1988 and 1989 foaling seasons to determine the causes of reproductive loss in the mare. Placentitis (19.4%) and dystocia-perinatal asphyxia (19.5%) were the 2 most important causes of equine reproductive loss. The other causes (in decreasing order) were contracted foal syndrome and other congenital anomalies (8.5%), twinning (6.1%), improper separation of placenta (4.7%) torsion of umbilical cord (4.5%), placental edema (4.3%), equine herpesvirus abortion (3.3%), bacteremia (3.2%), fetal diarrhea (2.7%), other placental disorders (total of 6.0%), and miscellaneous causes (1.6%). A definitive diagnosis was not established in 16.9% of the cases submitted. Streptococcus zooepidemicus, Escherichia coli, Leptospira spp., and a nocardioform actinomycete were organisms most frequently associated with bacterial placentitis, and Aspergillus spp. was the fungus most often noted in mycotic placentitis. No viral placentitis was noticed in this series. Dystocia-perinatal asphyxia was mostly associated with large foals, maiden mares, unattended deliveries, and malpresentations. The results of this study indicate that in central Kentucky, the noninfectious causes of equine reproductive loss outnumber the infectious causes by an approximate ratio of 2:1, placental disorders are slightly more prevalent than nonplacental disorders, Leptospira spp. and a nocardioform actinomycete are 2 new important abortifacient bacteria in the mare, the occurrence of contracted foal syndrome is unusually frequent, the incidence of twin abortion has sharply declined, and torsion of the umbilical cord is an important cause of abortion in the mare.

Leptospirosis in Equine Fetuses, Stillborn Foals, and Placentas

Leptospirosis was diagnosed in 51 equine fetuses and 16 stillborn foals with gestational ages from 3½ to 11 months. Diagnosis was based on one or more of the following: positive fetal antibody titer, positive fluorescent antibody test, demonstration of spirochetes in kidney and/or placental sections stained by the Warthin-Starry technique, high leptospiral titers in aborting mares, or isolation of Leptospira spp. from fetal organs. Gross lesions were observed in 80.3% of the fetuses, stillborn foals, and placentas. Gross placental lesions included nodular cystic allantoic masses, edema, areas of necrosis of the chorion, and necrotic mucoid exudate coating the chorion. The liver (23 cases) was enlarged, mottled, and pale to yellow. The kidneys (seven cases) were swollen and edematous with pale white radiating streaks in cortex and medulla. Microscopic lesions were observed in 96% of fetuses, stillborn foals, and placentas. Placental lesions consisted of thrombosis, vasculitis, mixed inflammatory cell infiltration of the stroma and villi, cystic adenomatous hyperplasia of allantoic epithelium, and villous necrosis and calcification. Fetal lesions included hepatocellular dissociation, mixed leukocytic infiltration of the portal triads, giant cell hepatopathy, suppurative and nonsuppurative nephritis, pulmonary hemorrhages, pneumonia, and myocarditis. Spirochetes were demonstrated with the Warthin-Starry stain in the allantochorion and/or kidney of 69 of the 71 cases. Using the direct fluorescent antibody technique, 56/60 cases tested positively for leptospires. Leptospires were isolated from fetal tissues in 20/42 cases. Sixteen of the isolates were identified by restriction enzyme analysis as Leptospira interrogans serogroup Pomona serovar kennewicki; case Nos. 36 and 41 were serovar grippotyphosa. The other two isolates were not identified. Microagglutination titers against leptospires were demonstrated in the body fluid of 47/67 cases tested and titers ranged from 1:50 to greater than 1:1,638,400 against Leptospira interrogans serovars pomona, grippotyphosa, copenhageni, hardjo, canicola, and bratislava. Sixty-two of 71 aborting mares tested had titers ranging from 200 to greater than 3,276,800. Leptospiral antibody titers in the body fluid and gross and histopathologic lesions did not differ with age, breed, or sex or between fetuses and stillborn foals.

Prevalence and Serovars of Leptospira Involved in Equine Abortions in Central Kentucky during the 1990 Foaling Season

A study to determine the prevalence of leptospira-induced abortions in the central Kentucky equine population during the 1990 foaling season and to determine the leptospira serovars responsible was conducted. From July 1, 1989 through June 30, 1990, 32 (4.4%) of 726 submissions (fetuses, stillborn foals, and/or placentas) were diagnosed as leptospirosis by the fluorescent antibody test and/or microscopic agglutination test. Attempts were made to isolate leptospires from the fetal tissues and/or the dams urine in 31 of these cases. Leptospira interrogans serovar kennewicki was isolated from 11 (35.5%) and serovar grippotyphosa from 2 (6.5%) of the 31 cases. Of 12 cases that were culture negative with serologically positive fetal fluids, 8 had titers against serovar pomona, 1 against bratislava, 1 against grippotyphosa, 1 against hardjo, and 1 against both bratislava and pomona.

Phylogenetic relationship of Sarcocystis neurona to other members of the family Sarcocystidae based on small subunit ribosomal RNA gene sequence

Sarcocystis neurona is a coccidial parasite that causes a neurologic disease of horses in North and South America. The natural host species are not known and classification is based on ultrastructural analysis. The small subunit ribosomal RNA (SSURNA) gene of S. neurona was amplified using polymerase chain reaction techniques and sequenced by Sanger sequencing reactions. The sequence was compared with partial sequences of S. muris, S. gigantea, S. tenella, S. cruzi, S. arieticanis, S. capracanis, Toxoplasma gondii, Eimeria tenella, and Cryptosporidium parvum. Alignments of available sites for all 10 species and alignments of the entire SSURNA sequence of S. neurona, S. muris, S. cruzi, T. gondii, and C. parvum were performed. Alignments were analyzed using maximum parsimony and maximum likelihood methods to determine relative phylogeny of these organisms. These analyses confirmed placement of S. neurona in the genus Sarcocystis and suggested a close relationship to S. muris, S. gigantea, and T. gondii. Molecular phylogeny suggests that Sarcocystis spp., which utilize the dog (Canis familiaris) as the definitive host, evolved from a common ancestor, whereas those species (including T. gondii) that utilize the cat (Felis domesticus) as the definitive host evolved from another common ancestor. This suggests a possible definitive host for S. neurona.

Histoplasmosis in horses

Histoplasmosis was diagnosed in nine horses during 1986-1990. The infection with Histoplasma capsulatum caused granulomatous placentitis and abortion in one mare in the 7th month of gestation and three mares in the 10th month. Four newborn foals died from severe granulomatous pneumonia within a few days of birth; and a weanling thoroughbred developed granulomatous pneumonia and lymphadenitis at 5 months of age.

Microbiologic and pathologic findings in an epidemic of equine pericarditis

During the spring and summer of 2001 and in association with the mare reproductive loss syndrome, 22 terminal and 12 clinical cases of equine pericarditis were diagnosed in central Kentucky. Actinobacillus species were the principal isolates from 8 of 10 nontreated, terminally affected and 3 of 10 clinically affected horses. Enterococcus faecalis and Streptococcus zooepidemicus were cultured from the remaining 2 nontreated terminal cases. No viruses were isolated in tissue culture. Nucleic acid of equine herpesvirus-2 was detected in pericardial and tracheal wash fluids of 3 and 1 individuals, respectively. Microscopic alterations in sections of heart and parietal pericardium were consistent with chronic fibrinous bacterial pericarditis. This report confirms a significant role of Actinobacillus species in equine pericarditis and describes an epidemic of this infrequently observed syndrome in the horse.

Transitional cell carcinoma of the urinary bladder in a Thoroughbred, with intra-abdominal dissemination.

A 14-year-old Thoroughbred gelding with a history of acute onset of hematuria was presented for necropsy. Transitional cell carcinoma of the urinary bladder with intra-abdominal dissemination was diagnosed. Tumor masses were observed on the splenic capsule and surrounding the distal abdominal aorta. Tumor cells showed diffuse cytoplasmic reactivity for cytokeratin but were negative for epithelial membrane antigen, carcinoembryonic antigen, tumor-associated glycoprotein 72, and vimentin.

Equine abortion and premature birth associated with Cellulosimicrobium cellulans infection

During the 2002 and 2003 foaling seasons, Cellulosimicrobium (Cellumonas) cellulans (formerly Oerskovia xanthineolytica) was the principal microorganism isolated from fetal tissues or placentas from cases of equine abortion, premature birth, and term pregnancies. Significant pathologic findings included chronic placentitis and pyogranulomatous pneumonia. In addition, microscopic and macroscopic alterations in the allantochorion from 4 of 7 cases of placentitis were similar to those caused by Crossiella equi and other nocardioform bacteria. This report confirms a causative role of C. cellulans infection in equine abortion.

Immunohistochemical Diagnosis of Protozoan Parasites in Lesions of Equine Protozoal Myeloencephalitis

asite also differed structurally from Caryospora sp. because gamonts were not found and schizonts and merozoites were much larger than those of Caryospora sp. In structure, the parasite in the present case resembles the Sarcocystis parasite that causes fatal encephalomyelitis in horses, cattle, and sheep. Although the central nervous system in the infected dog was not examined, its litter-mate died of protozoan encephalomyelitis. 4 Acknowledgements. We thank John Jenkins and Eva Kovats for technical assistance. Montana State University, Agricultural Experiment Station Journal series No. 525847.